Hawaii emergency officials said on Saturday an alert about an incoming ballistic missile threat was a false alarm.
The alert stated there was a threat “inbound to Hawaii” and said residents should seek shelter. “This is not a drill,” it added.
The alert caused a panic when it went to people’s cellphones on Saturday morning.
Tensions between the Trump administration and nuclear-armed North Korea have increased over the past year, over fears that the regime in Pyongyang may be able to reach the US mainland with a nuclear-armed missile.
Hawaiian authorities have been preparing and testing early warning systems.
On Saturday in western Oahu people ran out of buildings into the street, some wearing nothing but slippers. According to a witness, some took shelter in the basement of a parking structure, where people cried and children huddled on rolls of fabric.
Approximately 30 minutes later, authorities said the alert was a mistake.
Many in the parking shelter hugged, cried, shook and prepared to head back outside. Others said they would remain undercover until they received confirmation from the coast guard that all was safe.
Hawaii Emergency Management Agency spokesman Richard Rapoza said it was not clear what caused the alert to go out and the agency was investigating.
Jamie Malapit, owner of a Honolulu hair salon, told the Associated Press he was still in bed when the phone started going off “like crazy”. He thought it was a tsunami warning at first.
“I woke up and saw missile warning and thought no way. I thought ‘No, this is not happening today,”’ Malapit said. He was still “a little freaked out” and feeling paranoid even after hearing it was a false alarm.
“I went from panic to semi panic and ‘Are we sure?”’ he said.
The US representative Tulsi Gabbard tweeted that the alert was an error, writing: “HAWAII – THIS IS A FALSE ALARM. THERE IS NO INCOMING MISSILE TO HAWAII. I HAVE CONFIRMED WITH OFFICIALS THERE IS NO INCOMING MISSILE.”
A White House statement said Donald Trump had been “briefed on the state of Hawaii’s emergency management exercise”.